As I walked home late yesterday afternoon, the temperature in Columbia was 108 degrees F, the highest I have ever experienced in the American Midwest. A southwest wind was bringing hot, relatively dry air into the Heartland as the high pressure dome had dropped a bit to our southeast, placing Central Missouri along its northwest edge.
Highs above 100 degrees F are unusual in humid areas such as Florida and the Gulf Coast since water vapor decreases the density of the air and caps its capacity to retain heat. Dry air, typical of the American Southwest and other desert regions, is dense and is thus capable of reaching temperatures well above the century mark. Indeed, yesterday's blast furnace was remniscent of past summer visits to Phoenix; by 9 PM, the local temperature was still 98 F and, at dawn this morning, it had only dipped to 78.
Fortunately, a "cold front" will keep us in the mid 90s today and, by the middle of next week, highs are expected to remain in the 80s; following our prolonged heat wave, that will feel like autumn. While many are inclined to blame global warming for this intense summer heat, our last two winters were especially severe and this spring was exceptionally cool and damp. Stagnant weather patterns are the primary culprits for extreme variation from "average conditions;" of course, over time, climate change might redefine what is typical.
